The ES-3A Shadow variant of the basic S-3 Viking airframe was a short-lived but immensely valuable and capable platform optimized for signals capture and analysis.

The heart of the Shadow was an avionics suite based on the Aries II system of the land-based EP-3E Orion. The Shadow’s fuselage was packed with sensor stations and processing equipment and the exterior that supported over 60 antennas. The ES-3A Shadow crew comprised of a pilot, an naval flight officer, and two systems operators. Advanced sensor, navigation and communications systems allowed the Shadow’s four-person crew to collect extensive data and distribute high-quality information through a variety of channels to the carrier battle group. This gave the battle group commander a clear picture of potential airborne, surface and sub-surface threats. Missions flown by the detachment included over-the-horizon (OTH) targeting, strike support, war at sea and reconnaissance.

The ES-3A was considered a direct replacement for the EA-3B Skywarrior, yet had the same flight characteristics as the base Viking albeit with a slight decrease in top end speed.  It was also capable of providing aerial refueling in addition to its electronic work.

Two squadrons, VQ-5 and VQ-6, were established in 1991 with one based on each coast of the US.  In total, 16 Vikings were converted to the ES-3A configuration and they were typically operated two aircraft per deployed carrier.  The squadrons were disestablished in 1999.